Stack structures in electronic devices including passivation layers for distributing compressive force

ABSTRACT

Structures, methods and devices are disclosed, related to improved stack structures in electronic devices. In some embodiments, a stack structure includes a pad implemented on a substrate, the pad including a polymer layer having a side that forms an interface with another layer of the pad, the pad further including an upper metal layer over the interface, the upper metal layer having an upper surface. In some embodiments, the stack structure also includes a passivation layer implemented over the upper metal layer, the passivation layer including a pattern configured to provide a compressive force on the upper metal layer to thereby reduce the likelihood of delamination at the interface, the pattern defining a plurality of openings to expose the upper surface of the upper metal layer.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims priority to U.S. Provisional Application No.62/044,302 filed Aug. 31, 2014, entitled IMPROVED STACK STRUCTURES INELECTRONIC DEVICES, the disclosure of which is hereby expresslyincorporated by reference herein in its entirety.

BACKGROUND

The present disclosure relates to bonding stack structures forparticular semiconductor packaging applications.

DESCRIPTION OF THE RELATED ART

Some semiconductor chip packages use metallic bumps to allow forelectrical connections to other devices. These bumps are formed overopenings in a protective layer over a respective semiconductor chip.

SUMMARY

In accordance with some implementations, the present disclosure relatesto a stack structure including a pad implemented on a substrate, the padincluding a polymer layer having a side that forms an interface withanother layer of the pad, the pad further including an upper metal layerover the interface, the upper metal layer having an upper surface. Thestack structure also includes a passivation layer implemented over theupper metal layer, the passivation layer including a pattern configuredto provide a compressive force on the upper metal layer to therebyreduce the likelihood of delamination at the interface, the patterndefining a plurality of openings to expose the upper surface of theupper metal layer.

In some embodiments, the stack structure further includes a metalstructure implemented over the pad such that the metal structure isconnected to the exposed upper surface of the upper metal layer throughthe plurality of openings of the passivation layer. In someimplementations, the other layer of the pad is a metal layer such thatthe interface is between the polymer layer and the metal layer. In someembodiments, the metal layer is below the upper metal layer, and in someimplementations, the upper metal layer is the metal layer forming theinterface with the polymer layer.

In some embodiments, the polymer layer of the stack structure has atensile film stress property, and in some implementations the polymerlayer includes polyimide, benzocyclobutene (BCB), or polybenzoxazole(PBO). In some embodiments, the passivation layer of the stack structureincludes a silicon nitride layer.

In some embodiments, the pattern defining the plurality of openings ofthe passivation layer, is configured to function as a strap or a netover the upper metal layer to thereby provide the compressive force onthe upper metal layer. In some embodiments, the strap or the net of thepattern is substantially contiguous around the plurality of openings.

In some implementations, the substrate is a semiconductor substrate, andin some embodiments, the semiconductor substrate is a flip-chipsubstrate. In some embodiments, the pad of the stack structure is a bumppad and the metal structure is a metal bump. In some implementations,the semiconductor substrate is a base wafer layer having an integratedcircuit (IC), and in some embodiments, the stack structure is configuredto form a ring on the base wafer layer, the ring defining an inner areadimensioned to accommodate a device, the ring further configured toallow mounting of a cap wafer to substantially enclose the inner area.

The present disclosure also relates to a method for fabricating a stackstructure. The method includes providing a substrate, forming a pad onthe substrate such that the pad includes a polymer layer having a sidethat forms an interface with another layer of the pad, the pad furtherincluding an upper metal layer over the interface, the upper metal layerhaving an upper surface, forming a passivation layer over the uppermetal layer, and patterning the passivation layer to yield a pluralityof openings to expose the upper surface of the upper metal layer, and toprovide a compressive force on the upper metal layer to thereby reducethe likelihood of delamination at the interface.

In some implementations, the method further comprises forming a metalstructure over the pad such that the metal structure is connected to theexposed upper surface of the upper metal layer through the plurality ofopenings of the passivation layer.

According to some implementations, a chip is disclosed, having asubstrate layer. The chip also includes a plurality of connectionstructures implemented on a surface of the substrate layer, eachconnection structure including a pad, where the pad includes a polymerlayer having a side that forms an interface with another layer of thepad, the pad further including an upper metal layer over the interface,the upper metal layer having an upper surface, the connection structurefurther including a passivation layer implemented over the upper metallayer, the passivation layer including a pattern configured to provide acompressive force on the upper metal layer to thereby reduce thelikelihood of delamination at the interface, the pattern defining aplurality of openings to expose the upper surface of the upper metallayer, the connection structure further including a metal structureimplemented over the pad such that the metal structure is connected tothe exposed upper surface of the upper metal layer through the pluralityof openings of the passivation layer.

In some embodiments, the chip is a flip-chip, and in some embodiments,the chip is a MEMS device. In some embodiments, the chip is anintegrated passive device (IPD). In some implementations, the substratelayer includes a semiconductor die, while in some implementations, thesemiconductor die includes an integrated circuit (IC), and in someimplementations, the IC is configured to provide radio-frequency (RF)functionality.

In some embodiments, the substrate layer of the chip includes asemi-insulating layer, and in some embodiments, the semi-insulatinglayer includes a passive circuit. In some embodiments, thesemi-insulating layer includes gallium arsenide (GaAs). In someembodiments, the substrate layer of the chip includes an insulatorlayer, and in some embodiments, the insulator layer includes glass orsapphire.

The present disclosure also relates to a method for fabricating aflip-chip. The method includes providing a semiconductor die having anintegrated circuit (IC), and forming a plurality of connectionstructures on a surface of the die such that each connection structureincludes a pad, the pad including a polymer layer having a side thatforms an interface with another layer of the pad, the pad furtherincluding an upper metal layer over the interface, where the upper metallayer has an upper surface. The method further includes forming apassivation layer over the upper metal layer, patterning the passivationlayer to yield a plurality of openings to expose the upper surface ofthe upper metal layer and to provide a compressive force on the uppermetal layer to thereby reduce the likelihood of delamination at theinterface, and forming a metal structure over the pad such that themetal structure is connected to the exposed upper surface of the uppermetal layer through the plurality of openings of the passivation layer.

Another aspect of the present disclosure includes a radio-frequency (RF)apparatus including a base wafer having an integrated circuit (IC)configured to provide RF functionality and a cap wafer implemented overthe base wafer. The RF apparatus includes a ring structure implementedto join the cap wafer to the base wafer to yield a hermetic cavity, thering structure including a pad, the pad including a polymer layer havinga side that forms an interface with another layer of the pad, the padfurther including an upper metal layer over the interface, the uppermetal layer having an upper surface, the ring structure furtherincluding a passivation layer implemented over the upper metal layer,the passivation layer including a pattern configured to provide acompressive force on the upper metal layer to thereby reduce thelikelihood of delamination at the interface, the pattern defining aplurality of openings to expose the upper surface of the upper metallayer, the ring structure further including a metal structureimplemented over the pad such that the metal structure is connected tothe exposed upper surface of the upper metal layer through the pluralityof openings of the passivation layer.

In some embodiments, the cap wafer of the RF apparatus includes an IC,and in some embodiments, the IC of the cap wafer is at least partiallyconnected electrically to the IC of the base wafer through the ringstructure. In some implementations, the RF apparatus further includes adevice implemented within the hermetic cavity.

In some embodiments, the device is built on, or a part of, the IC of thebase wafer of the RF apparatus. In some embodiments, the device is aMEMS device, and in some embodiments, the device is mounted on the basewafer. In some embodiments, the device of the RF apparatus is a surfaceacoustic wave (SAW) device, a bulk acoustic wave (BAW) device, or a filmbulk acoustic resonator (FBAR) device. In some embodiments, the deviceis an RF filter.

According to some implementations, the present disclosure relates to amethod for fabricating a radio-frequency (RF) apparatus. The methodincludes providing a base wafer having an integrated circuit (IC)configured to provide RF functionality. The method also includes forminga ring structure on the base wafer such that the ring structure includesa pad, the pad including a polymer layer having a side that forms aninterface with another layer of the pad, the pad further including anupper metal layer over the interface, the upper metal layer having anupper surface, the ring structure further including a passivation layerimplemented over the upper metal layer, the passivation layer includinga pattern configured to provide a compressive force on the upper metallayer to thereby reduce the likelihood of delamination at the interface,the pattern defining a plurality of openings to expose the upper surfaceof the upper metal layer, the ring structure further including a metalstructure implemented over the pad such that the metal structure isconnected to the exposed upper surface of the upper metal layer throughthe plurality of openings of the passivation layer, and mounting a capwafer on the ring structure to yield a hermetic cavity.

In some implementations, the method includes mounting a device on thebase wafer prior to the mounting of the cap wafer. In some embodiments,the mounting of the device includes mounting a surface acoustic wave(SAW) device, a bulk acoustic wave (BAW) device, or a film bulk acousticresonator (FBAR) device on the base wafer.

The present disclosure further describes a radio-frequency (RF) moduleincluding a packaging substrate configured to receive a plurality ofcomponents, and an RF apparatus mounted on the packaging substrate, theRF apparatus including a stack structure having a pad, the pad includinga polymer layer having a side that forms an interface with another layerof the pad, the pad further including an upper metal layer over theinterface, the upper metal layer having an upper surface, the stackstructure further including a passivation layer implemented over theupper metal layer, the passivation layer including a pattern configuredto provide a compressive force on the upper metal layer to therebyreduce the likelihood of delamination at the interface, the patterndefining a plurality of openings to expose the upper surface of theupper metal layer, the stack structure further including a metalstructure implemented over the pad such that the metal structure isconnected to the exposed upper surface of the upper metal layer throughthe plurality of openings of the passivation layer.

In some embodiments, the RF apparatus of the RF module is a flip-chip.In some embodiments, the stack structure of the RF apparatus is aconnection structure configured to facilitate mounting of the flip-chip.In some implementations, the RF apparatus is an apparatus having ahermetic cavity. In some implementations, the stack structure is a ringstructure that interconnects a base wafer and a cap wafer to yield thehermetic cavity.

According to some implementations, the present disclosure relates to awireless device including an antenna configured to transmit or receive aradio-frequency (RF) signal, and an RF apparatus configured to processthe RF signal, the RF apparatus including a stack structure having apad, the pad including a polymer layer having a side that forms aninterface with another layer of the pad, the pad further including anupper metal layer over the interface, the upper metal layer having anupper surface, the stack structure further including a passivation layerimplemented over the upper metal layer, the passivation layer includinga pattern configured to provide a compressive force on the upper metallayer to thereby reduce the likelihood of delamination at the interface,the pattern defining a plurality of openings to expose the upper surfaceof the upper metal layer, the stack structure further including a metalstructure implemented over the pad such that the metal structure isconnected to the exposed upper surface of the upper metal layer throughthe plurality of openings of the passivation layer.

In some implementations, the RF apparatus of the wireless device is aflip-chip. In some implementations, the stack structure of the RFapparatus is a connection structure configured to facilitate mounting ofthe flip-chip. In some embodiments, the RF apparatus is an apparatushaving a hermetic cavity. In some embodiments, the stack structure ofthe RF apparatus is a ring structure that interconnects a base wafer anda cap wafer to yield the hermetic cavity. In some embodiments, the RFapparatus of the wireless device has one or more other qualities of anRF apparatus, a stack structure or chip, as described in the presentdisclosure.

For purposes of summarizing the disclosure, certain aspects, advantagesand novel features of the inventions have been described herein. It isto be understood that not necessarily all such advantages may beachieved in accordance with any particular embodiment of the invention.Thus, the invention may be embodied or carried out in a manner thatachieves or optimizes one advantage or group of advantages as taughtherein without necessarily achieving other advantages as may be taughtor suggested herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example stack structure having a plurality of layersformed on a semiconductor substrate, in accordance with someembodiments.

FIG. 2 shows an example of a stack being delaminated due to a shearforce, in accordance with some embodiments.

FIGS. 3A-3D show side sectional views of examples of bump pads havingdifferent stack configurations, in accordance with some embodiments

FIGS. 4A-4D show examples of metal bumps formed on the correspondingbump pads of FIG. 3A-3D, in accordance with some embodiments.

FIG. 5 shows a plan view of an example opening in a passivation layerformed over a bump pad, in accordance with some embodiments.

FIG. 6 shows an example of a bump pad with a reduced exposed metalsurface, in accordance with some embodiments.

FIG. 7 shows an example bump pad with a strip of passivation through themiddle of a metal surface of the pad, in accordance with someembodiments.

FIG. 8 shows an example bump pad with a strip of passivation through themiddle of a metal surface of the pad, in accordance with someembodiments.

FIG. 9 shows an example bump pad with a plurality of strips ofpassivation crossing over the metal surface of the pad, in accordancewith some embodiments.

FIG. 10 shows an example bump pad with a plurality of strips ofpassivation crossing over the metal surface of the pad in a grid-likeformation, in accordance with some embodiments.

FIG. 11 shows an example bump pad with a plurality of rectangles ofpassivation offset in a brick formation, in accordance with someembodiments.

FIG. 12 shows an example bump pad with a plurality of shapes ofpassivation in various sizes, in accordance with some embodiments.

FIGS. 13A-13D show side sectional views of examples of bump pads havingdifferent stack configurations, in accordance with some embodiments.

FIGS. 14A-14D show examples of metal bumps formed on the correspondingbump pads of FIGS. 13A-13D, in accordance with some embodiments.

FIGS. 15A and 15B show a plan view and a side sectional view of ahermetic cavity structure implemented on a base layer, in accordancewith some embodiments.

FIGS. 16A and 16B show a plan view and a side sectional view of a padstructure implemented on a base layer, in accordance with someembodiments.

FIGS. 17A and 17B show a plan view and a side sectional view of ahermetic cavity structure that is similar to the example of FIGS. 15Aand 15B, but with the pad structure as described in reference to FIGS.16A and 16B, in accordance with some embodiments.

FIG. 18 shows a process that can be implemented to form a robust stackstructure, in accordance with some embodiments.

FIG. 19 shows a process that can be implemented to form a robust stackstructure, in accordance with some embodiments.

FIG. 20 shows a process that can be implemented to manufacture a numberof devices, in accordance with some embodiments.

FIG. 21 shows a process that can be implemented to fabricate a cavitystructure, in accordance with some embodiments.

FIG. 22 shows an example flip-chip having a plurality of bumpstructures, in accordance with some embodiments.

FIG. 23 shows an example product with a hermetic cavity device, a cavityformed by a base layer, a ring structure and a cap layer.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

The headings provided herein, if any, are for convenience only and donot necessarily affect the scope or meaning of the claimed invention.

Disclosed are devices and methods related to improved stack structuresthat can be implemented on semiconductor substrates. FIG. 1 shows anexample stack structure 100 having a plurality of layers 102 a-102 cformed on a semiconductor substrate 104. Among such layers, there may beone or more inter-layer interfaces that are mechanically weaker thanother interfaces. For example, suppose that either or both interfaces(with the upper layer 102 c and/or the lower layer 102 a) associatedwith the middle layer 102 b is/are relatively weak due to one or morereasons. With such weak interface(s), the stack 100 can be damaged(e.g., delaminated) when subjected to a force (e.g., a shear force).

FIG. 1 further shows that in some embodiments, a compressive force(depicted as an arrow 108) can be applied above such weak interface(s)to reduce mechanical damage such as delamination of the stack 100. Forexample, such a compressive force can be implemented on top of the stack100 so as to pin down the stack 100 and thereby reduce the likelihood ofdelamination. Examples of such compressive force applied to differentstack structures are described herein in greater detail.

FIG. 2 shows an example of a stack being delaminated due to a shearforce 110. For the purpose of description of FIG. 2, suppose that threeexample layers 102 a-102 c form the stack, and a relatively largestructure 112 is implemented over the stack. Due to the shear force 110being applied to the structure 112, the stack is shown to delaminatebetween the layers 102 b and 102 c, thereby damaging the stackstructure.

Examples of the foregoing delamination can include semiconductorfabrication applications (e.g., silicon and gallium arsenide (GaAs)process technology) where polymers are typically used as inter-leveldielectric and/or as buffer stress and mechanical protection layers.These polymers can include, for example, polyimide, benzocyclobutene(BCB), polybenzoxazole (PBO), and others. Many of these polymerstypically have tensile film stress and are known to have relatively weakadhesion to many other materials such as metals and other dielectricsused in semiconductor technology.

Furthermore, due to flow characteristics of polymers, semiconductorwafers fabricated with polymer inter-level dielectric typically resultin non-planar surfaces and topography that can be as large as theunderlying device topography. Such non-planar surface and topographyusually results in additional stress and weak points at some areas,including, for example, at the interfaces where the polymer is incontact with its neighboring layers.

When used for flip-chip applications, the foregoing semiconductor waferstypically have bump metal pads on each die onto which metal bumps are tobe formed. These bump pads typically have a stack structure, and aretypically covered with final passivation or topcoat layer (e.g., siliconnitride film) that has a relatively high compressive stress property.The passivation layer is then patterned to open an underlying metal tothereby yield the bump pads.

For each bump pad, there is typically a single large opening having ashape such as an oval or a polygon (e.g., a rectangle or an octagon).However, due to the poor adhesion of one or more polymer layers belowthe exposed metal layer, and/or topography characteristics of underlyingfeatures in the bump pad, poor bump reliability can result when usingsuch large openings. For example, bumps formed on such bump pads caneasily be sheared off from the die.

In the context of the polymer inter-level layers in the foregoingexample, the layer 102 b of FIG. 2 can be a polymer layer, and thelayers 102 a and 102 c can be metal layers. Due to the polymer layer 102b having a relatively weak adhesion property with the metal layers (102a, 102 c), the interface between the layers 102 a (metal) and 102 b(polymer) is shown to fail.

FIGS. 3A-3D show side sectional views of examples of bump pads havingdifferent stack configurations, where one or more interfaces betweenpolymer inter-level layer(s) and metal layers can allow relatively easydelamination of the bump pads. FIGS. 4A-4D show examples of metal bumpsformed on the corresponding bump pads of FIGS. 3A-3D. Each of theresulting bump assemblies can suffer from delamination as in FIG. 2 whensubjected to, for example, a shear force.

In each of the example bump pads of FIGS. 3A-3D, a passivation layer 122(e.g., silicon nitride) having high compressive stress property isprovided. However, a single large opening is formed in the passivationlayer 122 to expose and provide access to an upper surface 123 of theupper-most metal layer for mounting of the bump metal. Accordingly, thelayers underneath such an opening do not benefit from the compressiveforce provided by the passivation layer 122. As further shown in FIGS.4A-4D, when the corresponding metal bump is attached to the bump pad,the passivation layer 122 provides little or no resistance to a shearforce applied to the metal bump.

In the example of FIG. 3A, a bump pad 120 a is shown to include a stackimplemented on a semiconductor substrate. More particularly, the stackincludes a first metal layer (M1) formed on the semiconductor substrate.The M1 layer is covered with a first polymer layer (P1), and a secondmetal layer (M2) is formed above the P1 layer, such that the M1 and M2layers are separated by the P1 layer. A second polymer layer (P2) isshown to be formed over the M2 layer, and an opening in the P2 layer isformed over the M2 layer. A third metal layer (M3) is shown to be formedover the M2 layer such that the M2 and M3 layers are in contact. Apassivation layer 122 such as a silicon nitride layer is shown to beformed over the foregoing stack and the region surrounding the stack. Anopening is formed in the silicon nitride layer 122 so as to expose theupper surface 123 of the M3 layer.

In the example of FIG. 4A, a metal bump 128 is shown to be formed on thebump pad 120 a of FIG. 3A. More particularly, an under bump metal (UBM)layer 126 is shown to be formed over the opening in the passivationlayer 122 so as to cover and be in contact with the upper surface 123 ofthe M3 layer. The metal bump 128 is shown to be formed over the UBMlayer 126, and a solder metal layer 130 is shown to be formed over themetal bump 128.

As described herein, metal-to-metal interfaces are relatively strong,and polymer-to-metal interfaces are relatively weak. Accordingly,metal-to-metal interfaces between the solder metal layer 130 and themetal bump 128, between the metal bump 128 and the UBM layer 126,between the UBM layer 126 and the M3 layer, and between the M3 layer andthe M2 layer are relatively strong; and polymer-to-metal interfacesbetween the M2 layer and the P1 layer, and between the P1 layer and theM1 layer are relatively weak. Thus, when the metal bump 128 and/or thebump pad 120 a are subjected to a force such as a shear force,delamination will likely occur at either or both of the interfacesassociated with the P1 layer.

In the example of FIG. 3B, a bump pad 120 b is shown to include a stackimplemented on a semiconductor substrate. More particularly, the stackincludes a first metal layer (M1) formed on the semiconductor substrate.A second metal layer (M2) is formed above the M1 layer, such that the M1and M2 layers are in contact. A polymer layer (P2) is shown to be formedover the M2 layer. A third metal layer (M3) is shown to be formed overthe P2 layer such that the M2 and M3 layers are separated by the P2layer. A passivation layer 122 such as a silicon nitride layer is shownto be formed over the foregoing stack and the region surrounding thestack. An opening is formed in the silicon nitride layer 122 so as toexpose the upper surface 123 of the M3 layer.

In the example of FIG. 4B, a metal bump 128 is shown to be formed on thebump pad 120 b of FIG. 3B. More particularly, an under bump metal (UBM)layer 126 is shown to be formed over the opening in the passivationlayer 122 so as to cover and be in contact with the upper surface 123 ofthe M3 layer. The metal bump 128 is shown to be formed over the UBMlayer 126, and a solder metal layer 130 is shown to be formed over themetal bump 128.

In the examples shown in FIGS. 3B and 4B, metal-to-metal interfacesbetween the solder metal layer 130 and the metal bump 128, between themetal bump 128 and the UBM layer 126, between the UBM layer 126 and theM3 layer, and between the M2 layer and the M1 layer are relativelystrong; and polymer-to-metal interfaces between the M3 layer and the P2layer, and between the P2 layer and the M2 layer are relatively weak.Thus, when the metal bump 128 and/or the bump pad 120 b are subjected toa force such as a shear force, delamination will likely occur at eitheror both of the interfaces associated with the P2 layer.

In the example of FIG. 3C, a bump pad 120 c is shown to include a stackimplemented on a semiconductor substrate. More particularly, the stackincludes a first metal layer (M1) formed on the semiconductor substrate,and a first polymer layer (P1) formed over the M1 layer. A second metallayer (M2) is formed above the P1 layer, such that the M1 and M2 layersare separated by the P1 layer. A second polymer layer (P2) is shown tobe formed over the M2 layer. A third metal layer (M3) is shown to beformed over the P2 layer such that the M2 and M3 layers are separated bythe P2 layer. A passivation layer 122 such as a silicon nitride layer isshown to be formed over the foregoing stack and the region surroundingthe stack. An opening is formed in the silicon nitride layer 122 so asto expose the upper surface 123 of the M3 layer.

In the example of FIG. 4C, a metal bump 128 is shown to be formed on thebump pad 120 c of FIG. 3C. More particularly, an under bump metal (UBM)layer 126 is shown to be formed over the opening in the passivationlayer 122 so as to cover and be in contact with the upper surface 123 ofthe M3 layer. The metal bump 128 is shown to be formed over the UBMlayer 126, and a solder metal layer 130 is shown to be formed over themetal bump 128.

In the examples shown in FIGS. 3C and 4C, metal-to-metal interfacesbetween the solder metal layer 130 and the metal bump 128, between themetal bump 128 and the UBM layer 126, and between the UBM layer 126 andthe M3 layer are relatively strong; and polymer-to-metal interfacesbetween the M3 layer and the P2 layer, between the P2 layer and the M2layer, between the M2 layer and the P1 layer, and between the P1 layerand the M1 layer are relatively weak. Thus, when the metal bump 128and/or the bump pad 120 b are subjected to a force such as a shearforce, delamination will likely occur at one or more of the foregoinginterfaces associated with the P1 and P2 layers.

In the example of FIG. 3D, a bump pad 120 d is shown to include a stackimplemented on a semiconductor substrate. More particularly, the stackincludes metal layers M1 and M1′ are shown to be formed on thesemiconductor substrate. A polymer layer (P1) is shown to be formed overthe M1′ layer. A metal layer (M2) is shown to be formed above the P1layer, such that the M1′ and M2 layers are separated by the P1 layer. Apolymer layer P2 is shown to be formed over the M2 layer and the M1layer. A metal layer M3 is shown to be formed over the P2 layer suchthat the M3 layer is separated from each of the M2 layer and the M1layer by the P2 layer. A passivation layer 122 such as a silicon nitridelayer is shown to be formed over the foregoing stack and the regionsurrounding the stack. An opening is formed in the silicon nitride layer122 so as to expose the upper surface 123 of the M3 layer.

In the example of FIG. 4D, a metal bump 128 is shown to be formed on thebump pad 120 d of FIG. 3D. More particularly, an under bump metal (UBM)layer 126 is shown to be formed over the opening in the passivationlayer 122 so as to cover and be in contact with the upper surface 123 ofthe M3 layer. The metal bump 128 is shown to be formed over the UBMlayer 126, and a solder metal layer 130 is shown to be formed over themetal bump 128.

In the examples shown in FIGS. 3D and 4D, metal-to-metal interfacesbetween the solder metal layer 130 and the metal bump 128, between themetal bump 128 and the UBM layer 126, and between the UBM layer 126 andthe M3 layer are relatively strong; and polymer-to-metal interfacesbetween the M3 layer and the P2 layer, between the P2 layer and theM2/M1 layers, between the M2 layer and the P1 layer, and between the P1layer and the M1′ layer are relatively weak. Thus, when the metal bump128 and/or the bump pad 120 b are subjected to a force such as a shearforce, delamination will likely occur at one or more of the foregoinginterfaces associated with the P1 and P2 layers.

It is noted that the example bump pad 120 d shown in FIGS. 3D and 4D isdifferent from the example bump pads of FIGS. 3A-3C, in that the M3 andP2 layers have significant non-planar topographic features. Suchnon-planar features can result in stress and weak points at certainareas. Thus, the interface between the M3 layer and the P2 layer is alikely location of mechanical failure when the metal bump 128 issubjected to a shear force.

FIG. 5 depicts a plan view of an example opening in a passivation layer122 formed over a bump pad 120. Such an opening can be any of theopenings in the passivation layers (122) in the examples described inreference to FIGS. 3A-3D. For the purpose of description, suppose thatsuch an opening exposes substantially all of an upper surface 123 of theupper-most metal layer (e.g., M3 in FIGS. 3A-3D). As described herein,such an opening does not allow the compressive stress property of thepassivation layer 122 to be transferred effectively to the layersunderneath the exposed upper surface 123. Accordingly, one or more weakinterfaces underneath the exposed upper surface 123 remain susceptibleto delamination.

In some embodiments, an opening in a passivation layer can bedimensioned to cover some or all of a boundary portion of what wouldotherwise be exposed on a metal surface. Such a configuration canprovide compressive force along such a covered boundary portion, whichin turn can reduce the likelihood of delamination at one or moreunderlying interfaces.

FIG. 6 shows an example of a bump pad 150 where a passivation layer 152covers left and right edge portions of a metal surface 156, therebyyielding a reduced exposed metal surface 154. The metal surface 156 isdepicted in the context of the example of FIG. 5. However, it will beunderstood that other metal surface configurations and otheredge-coverage configurations can also be implemented. For example, theexample of FIG. 6 shows edge coverages on the opposing end portions of arectangular or oval shaped metal surface. In other configurations, suchedge coverages can also be implemented to, for example, provide coveragearound the entire perimeter of a given metal surface shape.

In the example of FIG. 6, the edge portions of the metal surface 156being compressed by the passivation layer 152 can reduce the likelihoodof delamination at one or more interfaces generally below the metalsurface. Greater amount of such an edge coverage can yield greatercompressive force on the bump pad; however, too much coverage cannegatively impact the quality of metal bump formation on the reducedarea of an exposed metal surface. In some embodiments, such an edgecoverage of the metal surface can be, for example, at least 5%, 10%,15%, 20%, 25%, 30%, 35%, 40%, 45%, or 50% of the area of the upper-mostmetal surface in the absence of a passivation layer.

In the example of FIG. 6, the edge coverage configuration generally doesnot provide a compressive force at or near the center portion of theexposed metal surface 154. In some applications, such compressive forcemay be desirable at one or more different locations (e.g., a centerportion) of a metal surface. FIGS. 7-14 show non-limiting examples ofvarious configurations where at least some compressive force can beprovided at one or more locations other than at or near the edgeportions of a metal surface. For the purpose of description, such ametal surface is depicted as the oval shaped example of FIG. 5. However,it will be understood that one or more features of the presentdisclosure can also be implemented for other shapes of metal surfaces.

FIGS. 7 and 8 show examples of bump pads 160 having a passivation layer162 which includes a strip 166 extending through a middle portion of ametal surface. In the example of FIG. 7, such a strip is shown to extendtop-to-bottom when viewed as shown. Accordingly, exposed portions 164 a,164 b of the metal surface are on the left and right, respectively, ofthe passivation layer strip 166. In the example of FIG. 8, such a stripis shown to extend left-to-right when viewed as shown. Accordingly,exposed portions 164 a, 164 b of the metal surface are above and below,respectively, of the passivation layer strip 166.

In the examples of FIGS. 7 and 8, the passivation layer strip 166 can beformed by patterning the exposed portions 164 a, 164 b during theformation of the passivation layer 162. For example, instead ofpatterning a single large opening to expose the metal surface, twoopenings corresponding to the exposed portions 164 a, 164 b can bepatterned.

In the example of FIGS. 7 and 8, the passivation layer strip 166 canstrap-down the middle portion of the metal surface so as to reduce thelikelihood of delamination at one or more underlying interfaces. At thesame time, the two exposed metal surfaces 164 a, 164 b allow formationof contact with, for example, a metal bump.

In some applications, it may be desirable to have more than one strip ofpassivation layer to provide more distributed strap-down functionality.Such strips can be arranged in a number of different ways. For example,a plurality of strips can be arranged to be generally parallel. Inanother example, and as shown in FIG. 9, a plurality of strips can bearranged in a crossing manner. More particularly, FIG. 9 shows anexample where the passivation layer (162) can include strips 166 a, 166b that generally form a cross pattern at or near the middle portion ofthe metal surface. Accordingly, four exposed portions (164 a, 164 b, 164c, 164 d) of the metal surface are defined at the four quadrants of thecross pattern. As described herein, such exposed portions of the metalsurface can allow formation of contact with, for example, a metal bump.

FIG. 10 shows an example where the passivation layer (162) can include aplurality of strips 166 extending along each of the horizontal andvertical directions (when viewed as shown in FIG. 10), so as to definean array of exposed portions 164 of the metal surface. In the example ofFIG. 10, such exposed portions 164 of the metal surface are shown toform a grid of checkerboard pattern.

In the example of FIG. 10, the grid pattern of the strips 166 of thepassivation layer 162 can function as a net formed over the bump pad160. Such a net can provide a compressive force on the bump pad 160,with the compressive force being distributed over the metal surface,while providing a pattern of exposed portions of the metal surface. Asdescribed herein, such exposed portions of the metal surface can allowformation of contact with, for example, a metal bump.

In the examples of FIGS. 7-10, various strips of passivation layers aredepicted as generally straight strips that extend horizontally and/orvertically (when viewed as shown). However, it will be understood that apatterned passivation layer that provides compressive force for a bumppad and also allows formation of a metal structure (such as a metalbump) thereon can include other types of patterns. FIGS. 11-12 showexamples of such other types of patterns.

In the example of FIG. 11, a passivation layer 162 can include a pattern166 so as to yield exposed portions 164 that form rows of stretchedrectangles. Such rows can be arranged in a brick pattern, where one rowof rectangles is offset from the next row of rectangles. Accordingly,such a pattern 166 of the passivation layer 162 can provide adistributed compressive force on the bump pad 160, while providing apattern of exposed portions (164) of the metal surface. As describedherein, such exposed portions of the metal surface can allow formationof contact with, for example, a metal bump.

FIG. 12 shows that in some embodiments, openings formed on a passivationlayer can have more than one shape, and/or more than one size. Forexample, a passivation layer 162 is shown to be patterned such that theresulting exposed portions 164 of the metal layer include a number ofdifferent sized rectangles, as well as irregular polygons. Such apattern 166 of the passivation layer 162 can provide a distributedcompressive force on the bump pad 160, while providing a pattern ofexposed portions (164) of the metal surface. As described herein, suchexposed portions of the metal surface can allow formation of contactwith, for example, a metal bump.

In the examples described in reference to FIGS. 7-12, the metal surfacesand the various opening shapes patterned in their respective passivationlayers are depicted as polygons. However, it will be understood thatother shapes can also be implemented for the metal surfaces and/or theopenings in the passivation layers.

FIGS. 13A-13D show side sectional views of examples of bump pads havingdifferent stack configurations, similar to the examples of FIGS. 3A-3D,but where a passivation layer having one or more features as describedin reference to FIGS. 6-12 can provide a compressive force on therespective bump pad and thereby reduce the likelihood of delamination atone or more underlying interfaces. FIGS. 14A-14D show examples of metalbumps formed on the corresponding bump pads of FIGS. 13A-13D.

In each of the example bump pads of FIGS. 13A-13D, a passivation layer162 (e.g., silicon nitride) having high compressive stress property isprovided. Such a passivation layer can extend over the uppermost metallayer with a pattern 166 having one or more openings (e.g., exposedportions 164), so as to provide a compressive force distributed over theuppermost metal layer. As mentioned, such a pattern (166) of thepassivation layer 162 also defines one or more exposed portions 164 ofthe metal surface that allows formation of a metal bump in contact withthe exposed portion(s) 164 of the metal surface.

In the example of FIG. 13A, a bump pad 160 is shown to include a stackimplemented on a semiconductor substrate. More particularly, the stackincludes a first metal layer (M1) formed on the semiconductor substrate.The M1 layer is covered with a first polymer layer (P1), and a secondmetal layer (M2) is formed above the P1 layer, such that the M1 and M2layers are separated by the P1 layer. A second polymer layer (P2) isshown to be formed over the M2 layer, and an opening in the P2 layer isformed over the M2 layer. A third metal layer (M3) is shown to be formedover the M2 layer such that the M2 and M3 layers are in contact. Apassivation layer 162 such as a silicon nitride layer, is shown to beformed over the foregoing stack and the region surrounding the stack.One or more openings defined by a pattern 166 of the passivation layer162 are shown to expose the upper surface of the M3 layer so as to allowformation of a metal feature thereon.

In the example of FIG. 14A, a metal bump 174 is shown to be formed onthe bump pad 160 of FIG. 13A. More particularly, an under bump metal(UBM) layer 172 is shown to be formed over the exposed portions 164 ofthe metal surface of M3 and the patterned portion 166 of the passivationlayer 162 so as to cover and be in contact with the exposed portions 164of the M3 layer. The metal bump 174 is shown to be formed over the UBMlayer 172, and a solder metal layer 176 is shown to be formed over themetal bump 174.

As described herein, metal-to-metal interfaces are relatively strong,and polymer-to-metal interfaces are relatively weak. Accordingly,metal-to-metal interfaces between the solder metal layer 176 and themetal bump 174, between the metal bump 174 and the UBM layer 172,between the UBM layer 172 and the exposed portions 164 of the M3 layer,and between the M3 layer and the M2 layer are relatively strong; andpolymer-to-metal interfaces between the M2 layer and the P1 layer, andbetween the P1 layer and the M1 layer are relatively weak. However, evenif the metal bump 174 and/or the bump pad 160 are subjected to a forcesuch as a shear force, likelihood of delamination (e.g., at either orboth of the interfaces associated with the P1 layer) is reduced by thepatterned coverage of the passivation layer 162 over the M3 layer.

In the example of FIG. 13B, a bump pad 160 is shown to include a stackimplemented on a semiconductor substrate. More particularly, the stackincludes a first metal layer (M1) formed on the semiconductor substrate.A second metal layer (M2) is formed above the M1 layer, such that the M1and M2 layers are in contact. A polymer layer (P2) is shown to be formedover the M2 layer. A third metal layer (M3) is shown to be formed overthe P2 layer such that the M2 and M3 layers are separated by the P2layer. A passivation layer 162 such as a silicon nitride layer is shownto be formed over the foregoing stack and the region surrounding thestack. One or more openings defined by a pattern 166 of the passivationlayer 162 are shown to expose the upper surface of the M3 layer so as toallow formation of a metal feature thereon.

In the example of FIG. 14B, a metal bump 174 is shown to be formed onthe bump pad 160 of FIG. 13B. More particularly, an under bump metal(UBM) layer 172 is shown to be formed over the exposed portions 164 ofthe metal surface of M3 and the patterned portion 166 of the passivationlayer 162 so as to cover and be in contact with the exposed portions 164of the M3 layer. The metal bump 174 is shown to be formed over the UBMlayer 172, and a solder metal layer 176 is shown to be formed over themetal bump 174.

As described herein, metal-to-metal interfaces are relatively strong,and polymer-to-metal interfaces are relatively weak. Accordingly,metal-to-metal interfaces between the solder metal layer 176 and themetal bump 174, between the metal bump 174 and the UBM layer 172,between the UBM layer 172 and the exposed portions 164 of the M3 layer,and between the M2 layer and the M1 layer are relatively strong; andpolymer-to-metal interfaces between the M3 layer and the P1 layer, andbetween the P1 layer and the M2 layer are relatively weak. However, evenif the metal bump 174 and/or the bump pad 160 are subjected to a forcesuch as a shear force, likelihood of delamination (e.g., at either orboth of the interfaces associated with the P1 layer) is reduced by thepatterned coverage of the passivation layer 162 over the M3 layer.

In the example of FIG. 13C, a bump pad 160 is shown to include a stackimplemented on a semiconductor substrate. More particularly, the stackincludes a first metal layer (M1) formed on the semiconductor substrate,and a first polymer layer (P1) formed over the M1 layer. A second metallayer (M2) is formed above the P1 layer, such that the M1 and M2 layersare separated by the P1 layer. A second polymer layer (P2) is shown tobe formed over the M2 layer. A third metal layer (M3) is shown to beformed over the P2 layer such that the M2 and M3 layers are separated bythe P2 layer. A passivation layer 162 such as a silicon nitride layer isshown to be formed over the foregoing stack and the region surroundingthe stack. One or more openings defined by a pattern 166 of thepassivation layer 162 are shown to expose the upper surface of the M3layer so as to allow formation of a metal feature thereon.

In the example of FIG. 14C, a metal bump 174 is shown to be formed onthe bump pad 160 of FIG. 13C. More particularly, an under bump metal(UBM) layer 172 is shown to be formed over the exposed portions 164 ofthe metal surface of M3 and the patterned portion 166 of the passivationlayer 162 so as to cover and be in contact with the exposed portions 164of the M3 layer. The metal bump 174 is shown to be formed over the UBMlayer 172, and a solder metal layer 176 is shown to be formed over themetal bump 174.

As described herein, metal-to-metal interfaces are relatively strong,and polymer-to-metal interfaces are relatively weak. Accordingly,metal-to-metal interfaces between the solder metal layer 176 and themetal bump 174, between the metal bump 174 and the UBM layer 172, andbetween the UBM layer 172 and the exposed portions 164 of the M3 layerare relatively strong; and polymer-to-metal interfaces between the M3layer and the P2 layer, between the P2 layer and the M2 layer, betweenthe M2 layer and the P1 layer, and between the P1 layer and the M1 layerare relatively weak. However, even if the metal bump 174 and/or the bumppad 160 are subjected to a force such as a shear force, likelihood ofdelamination (e.g., at one or more of the interfaces associated with theP1 and P2 layers) is reduced by the patterned coverage of thepassivation layer 162 over the M3 layer.

In the example of FIG. 13D, a bump pad 160 is shown to include a stackimplemented on a semiconductor substrate. More particularly, the stackincludes metal layers M1 and M1′ are shown to be formed on thesemiconductor substrate. A polymer layer (P1) is shown to be formed overthe M1′ layer. A metal layer (M2) is shown to be formed above the P1layer, such that the M1′ and M2 layers are separated by the P1 layer. Apolymer layer P2 is shown to be formed over the M2 layer and the M1layer. A metal layer M3 is shown to be formed over the P2 layer suchthat the M3 layer is separated from each of the M2 layer and the M1layer by the P2 layer. A passivation layer 162 such as a silicon nitridelayer is shown to be formed over the foregoing stack and the regionsurrounding the stack. One or more openings defined by a pattern 166 ofthe passivation layer 162 are shown to expose the upper surface of theM3 layer so as to allow formation of a metal feature thereon.

In the example of FIG. 14D, a metal bump 174 is shown to be formed onthe bump pad 160 of FIG. 13D. More particularly, an under bump metal(UBM) layer 172 is shown to be formed over the exposed portions 164 ofthe metal surface of M3 and the patterned portion 166 of the passivationlayer 162 so as to cover and be in contact with the exposed portions 164of the M3 layer. The metal bump 174 is shown to be formed over the UBMlayer 172, and a solder metal layer 176 is shown to be formed over themetal bump 174.

As described herein, metal-to-metal interfaces are relatively strong,and polymer-to-metal interfaces are relatively weak. Accordingly,metal-to-metal interfaces between the solder metal layer 176 and themetal bump 174, between the metal bump 174 and the UBM layer 172, andbetween the UBM layer 172 and the exposed portions 164 of the M3 layerare relatively strong; and polymer-to-metal interfaces between the M3layer and the P2 layer, between the P2 layer and the M2/M1 layers,between the M2 layer and the P1 layer, and between the P1 layer and theM1′ layer are relatively weak. However, even if the metal bump 174and/or the bump pad 160 are subjected to a force such as a shear force,likelihood of delamination (e.g., at one or more of the interfacesassociated with the P1 and P2 layers) is reduced by the patternedcoverage of the passivation layer 162 over the M3 layer.

It is noted that the example bump pad 160 shown in FIGS. 13D and 14D isdifferent from the example bump pads of FIGS. 13A-13C, in that the M3and P2 layers have significant non-planar topographic features. Suchnon-planar features can result in stress and weak points at certainareas. Thus, the interface between the M3 layer and the P2 layer is alikely location of mechanical failure when the metal bump 174 issubjected to a shear force. Accordingly, in some embodiments, thepatterned portion 166 of the passivation layer 162 can be configured toaccommodate such stressed and weak points.

Various examples described herein in reference to FIGS. 3-14 aregenerally related to bump pads and metal bumps implemented thereon.FIGS. 15-17 show that in some embodiments, one or more features of thepresent disclosure can also be implemented in other applications,including, for example, a stacked wall structure to form a cavity (e.g.,hermetic cavity) on a substrate such as a wafer.

FIGS. 15A and 15B show a plan view and a side sectional view of ahermetic cavity structure 200 implemented on a base layer 202 such as awafer. Although not shown, such a base wafer can include one or morecircuits. A stack structure 206 is shown to surround an inner area 210.Such a stack structure can include one or more features as describedherein. Such an inner area can be dimensioned to allow implementation ofone or more devices (depicted as 212) therein. Such a device may bebuilt on or be a part (e.g., a MEMS device) of the circuitry of the basewafer 202, may be a separate device (e.g., a SAW, BAW, or FBAR) that isattached to the surface of the base wafer 202, or any combinationthereof. As shown in FIG. 15B, the device 212 can be mounted on a metallayer 216 which is formed above a polymer layer. In some embodiments,such a polymer layer can be an extension of the P2 layer described inreference to FIGS. 3D and 4D.

A cap layer 204 such as a wafer is shown to be mounted on the stackstructure 206 so as to enclose the inner area 210 into a hermeticallysealed cavity. Such a cap wafer may be configured to provide sealingfunctionality, may contain one or more circuits configured to performsome desired function in conjunction with the base wafer, or anycombination thereof.

In the example of FIGS. 15A and 15B, the stack structure 206 is depictedas having a sectional configuration that is similar to the example ofFIGS. 3D and 4D. Accordingly, such a stack structure includes an uppersurface 208 of the M3 layer that is exposed before implementation of ametal layer functionally similar to the UBM layer. As described herein,such an exposed metal surface (depicted as 208 in FIG. 15A) generallydoes not provide a compressive force to resist delamination of one ormore underlying interfaces.

FIGS. 16A and 16B show a plan view and a side sectional view of a padstructure 224 implemented on a base layer 222 such as a wafer. Such apad structure can be utilized to build a hermetic cavity structure asdescribed herein. For the purpose of description, it will be assumedthat the base wafer 222 is similar to the base wafer 202 of FIGS. 15Aand 15B.

In the example of FIGS. 16A and 16B, the pad structure 224 is depictedas having a sectional configuration that is similar to the example ofFIGS. 13D and 14D. Accordingly, such a pad structure includes exposedportions 228 of the M3 layer defined by a patterned portion 226 of apassivation layer 232. As described herein, such a patterned coverage ofthe passivation layer over the metal surface provides a compressiveforce to resist delamination of one or more underlying interfaces.

As shown in FIGS. 16A and 16B, the pad structure 224 is shown to definean inner area 230 which can be dimensioned to allow implementation ofone or more devices therein. To facilitate such device(s), a polymerlayer (e.g., an extension of the P2 layer) can be implemented over thebase wafer 222.

FIGS. 17A and 17B show a plan view and a side sectional view of ahermetic cavity structure 240 that is similar to the example of FIGS.15A and 15B, but with the pad structure 224 as described in reference toFIGS. 16A and 16B. With the pattern of exposed openings, theinterface(s) underneath the M3 layer is/are less likely to delaminate,and at the same time, the exposed portions of the M3 layer can allowformation of metal-to-metal contact with a metal layer 250 which can befunctionally similar to the UBM layer (e.g., 172 in FIG. 14D). A metalring 252 can be formed over the metal layer 250. A cap layer 242 such asa wafer can be secured to the metal ring 252 through, for example, oneor more solder metal layers (e.g., 254, 256). In some embodiments, sucha cap wafer can be configured similar to the example of FIGS. 15A and15B.

In the example of FIGS. 17A and 17B, the pad structure 224 having thepatterned portion of the passivation layer (232 in FIG. 16B) allows thehermetic cavity structure 240 to be more robust than the example ofFIGS. 15A and 15B. As described herein, such robustness can be providedby a compressive force over one or more polymer-metal interfaces.

In the example of FIGS. 17A and 17B, a hermetic cavity 244 formedgenerally in the inner area of FIGS. 16A and 16B is shown to bedimensioned to allow implementation of one or more devices (depicted as246). The device 246 is shown to be mounted on a metal layer 248 whichis in turn applied over a polymer layer (e.g., polymer layer P2). Such adevice can be similar to the device 212 described in reference to FIGS.15A and 15B.

In the various examples of FIGS. 15-17, the cavities formed by theirrespective stack structures are described as being hermetic cavities. Itwill be understood that one or more features of the present disclosurecan be implemented in applications involving cavities that may or maynot have hermetic property. It will also be understood that one or morefeatures of the present disclosure can be implemented in applicationswhere stack structures do not necessarily form a complete ring around aninner area.

FIG. 18 shows a process 300 that can be implemented to form a robuststack structure having one or more features as described herein. Inblock 302, a stack structure can be formed. In block 304, a layer can beformed relative to the structure to provide a compressive form on thestack while allowing access to the stack. For example, the layer is apassivation layer, as described above with respect to FIGS. 3A to 17B.

FIG. 19 show a process 310 that can be implemented as a more specificexample of the process 300 of FIG. 18. In block 312, a substrate such asa wafer can be provided. In block 314, a stack structure can be formedon the wafer substrate, where the stack includes a polymer layer betweenfirst and second metal layers. In block 316, a passivation layer can beformed over the stack to provide a compressive force on the stack whileallowing an electrical connection to be made to an upper surface of thestack. The process 310 can further include block 318 where a conductivestructure can be formed over the passivation layer such that theconductive structure is electrically connected to the upper surface ofthe stack.

As described herein, the stack structure of block 314 can be, forexample, a bump pad of FIGS. 7-14, and the conductive structure of block318 can be, for example, a metal bump of FIGS. 14A-14D. As alsodescribed herein, the stack structure of block 314 can be, for example,a pad structure of FIGS. 16A and 16B, and the conductive structure ofblock 318 can be, for example, a metal ring of FIGS. 17A and 17B.

In some embodiments, a device having delamination-resistance asdescribed herein can be fabricated in a wafer form and be singulated.FIG. 20 shows a process 320 that can be implemented to manufacture anumber of such devices. In block 322, a wafer substrate can be provided.In block 324 a stack structure can be formed on each of a plurality ofregions on the wafer substrate, where each stack structure includes apolymer layer between first and second metal layers. In block 326, apassivation layer can be formed over the stack structures, andappropriate patterned openings can be formed over each stack structureto provide a compressive force on the stack structure while allowing anelectrical connection to be made to the upper surface of the stackstructure. In block 328, a metal structure such as a metal bump can beformed over the passivation layer of each stack structure, such that themetal structure is electrically connected to the upper surface of thestack structure. In block 330, the regions can be singulated to yield aplurality of individual die.

FIG. 21 shows a process 340 that can be implemented to fabricate acavity structure having one or more features as described herein. Inblock 324, a base wafer can be provided. In block 344, a pad structurecan be formed on the base wafer to facilitate the cavity, where the padstructure includes a polymer layer between first and second metallayers. In block 346, a passivation layer can be formed over the padstructure to provide a compressive force of the pad structure whileallowing an electrical connection to be made to an upper surface of thepad structure. In block 348, a ring structure can be formed over thepassivation layer such that the ring structure is electrically connectedto the upper surface of the pad structure. In block 350, a cap wafer canbe mounted over the ring structure to substantially seal the cavity.

In the example of FIG. 21, the sealed cavity can provide a hermeticcavity environment for one or more circuits and/or devices implementedtherein. In the context of a device being implemented in such a hermeticcavity, the device can be mounted on the base wafer at different stagesof the fabrication process 340 of FIG. 21. For example, the device canbe mounted on the base wafer before or after the formation of the padstructure. The device can also be mounted on the base wafer before orafter the formation of the ring structure.

FIGS. 22 and 23 show non-limiting examples of products that can includeand benefit from one or more features as described herein. FIG. 22 showsthat in some embodiments, a flip-chip 400 can include a plurality ofbump structures 402 configured to provide electrical connection and/ormounting functionalities. Such bump structures can include bump pads asdescribed herein, and metal bumps formed on such bump pads. Some or allof such bump structures can include a compressive force configuration(depicted as 404) as described herein to reduce the likelihood ofdelamination at one or more interfaces within the bump structures.

In some embodiments, the flip-chip 400 of FIG. 22 can be configured forradio-frequency (RF) applications. In other embodiments, a flip-chiphaving one or more features as described herein can also be implementedin other electronic applications.

In some embodiments, a flip-chip having bump structures as describedherein can include a substrate layer, and such bump structures can beimplemented on such a substrate layer. In some embodiments, thesubstrate layer can be a semiconductor layer (e.g., a semiconductordie). Such a semiconductor layer can include, for example, an integratedcircuit (IC). In some embodiments, the substrate layer can be asemi-insulating layer such as a gallium arsenide (GaAs) layer. Such asemi-insulating layer can include, for example, a passive circuit. Insome embodiments, the substrate layer can be an insulator layer such asglass or sapphire.

In the context of RF applications, one or more flip-chips as describedherein can be utilized in wireless devices. Such wireless devices caninclude, for example, a cellular phone, a smart-phone, a hand-heldwireless device with or without phone functionality, a wireless tablet,etc.

FIG. 23 shows that in some embodiments, a hermetic cavity device 410 caninclude a cavity 418 formed by a base layer 412, a ring structure 416,and a cap layer 414. Such a cavity can provide a hermetically sealedenvironment for a component 420.

In some embodiments, the ring structure 416 may or may not include acompressive force configuration (depicted as 422) as described herein.With such a compressive force configuration, the likelihood ofdelamination at one or more interfaces within the ring structure 416 canbe reduced.

In some embodiments, the base layer 412 can be a base wafer, and the caplayer 414 can be a cap wafer. Although the base wafer 412 is depicted ashaving the same lateral size as the cap wafer 414, it will be understoodthat the base wafer 412 can be larger, and can include one or more othercomponents mounted thereon with or without cavity(ies).

In some embodiments, the component 420 implemented within the cavity 418can be a device that is built on the base wafer 412, a part (e.g., aMEMS) of a circuitry of the base wafer 412, a separate device (such as aSAW, BAW, or FBAR) that is attached to the surface of the base wafer412, or any combination thereof. In some embodiments, hermetic cavitydevice 410 having such a device (e.g., component 420) can be configuredfor radio-frequency (RF) applications. In other embodiments, a hermeticcavity device having one or more features as described herein can alsobe implemented in other electronic applications.

In the context of RF applications, one or more hermetic cavity devicesas described herein can be utilized in wireless devices. Such wirelessdevices can include, for example, a cellular phone, a smart-phone, ahand-held wireless device with or without phone functionality, awireless tablet, etc.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense, as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” The word “coupled”, as generally usedherein, refers to two or more elements that may be either directlyconnected, or connected by way of one or more intermediate elements.Additionally, the words “herein,” “above,” “below,” and words of similarimport, when used in this application, shall refer to this applicationas a whole and not to any particular portions of this application. Wherethe context permits, words in the above Detailed Description using thesingular or plural number may also include the plural or singular numberrespectively. The word “or” in reference to a list of two or more items,that word covers all of the following interpretations of the word: anyof the items in the list, all of the items in the list, and anycombination of the items in the list.

The above detailed description of embodiments of the invention is notintended to be exhaustive or to limit the invention to the precise formdisclosed above. While specific embodiments of, and examples for, theinvention are described above for illustrative purposes, variousequivalent modifications are possible within the scope of the invention,as those skilled in the relevant art will recognize. For example, whileprocesses or blocks are presented in a given order, alternativeembodiments may perform routines having steps, or employ systems havingblocks, in a different order, and some processes or blocks may bedeleted, moved, added, subdivided, combined, and/or modified. Each ofthese processes or blocks may be implemented in a variety of differentways. Also, while processes or blocks are at times shown as beingperformed in series, these processes or blocks may instead be performedin parallel, or may be performed at different times.

The teachings of the invention provided herein can be applied to othersystems, not necessarily the system described above. The elements andacts of the various embodiments described above can be combined toprovide further embodiments.

While some embodiments of the inventions have been described, theseembodiments have been presented by way of example only, and are notintended to limit the scope of the disclosure. Indeed, the novel methodsand systems described herein may be embodied in a variety of otherforms; furthermore, various omissions, substitutions and changes in theform of the methods and systems described herein may be made withoutdeparting from the spirit of the disclosure. The accompanying claims andtheir equivalents are intended to cover such forms or modifications aswould fall within the scope and spirit of the disclosure.

What is claimed is:
 1. A stack structure comprising: a pad implementedon a substrate, the pad including a first stack including a first metallayer and a second stack including a second metal layer, the pad furtherincluding a polymer layer having a lower surface that forms an interfacewith the first metal layer of the first stack and the second metal layerof the second stack, and having a wall on a side of the polymer layer,the pad further including an upper metal layer over the polymer layer,the upper metal layer having an upper surface on which to implement ametal bump and having a wall on a side of the upper metal layer; and apassivation layer including first and second portions, the first portionconfigured to cover the wall of the upper metal layer and to cover thewall of the polymer layer, the first portion extending downwardfollowing the shape of the wall of the upper metal layer and the wall ofthe polymer layer, the second portion implemented over the upper metallayer, the second portion of the passivation layer including a patterndefining a plurality of openings in the second portion of thepassivation layer within a peripheral boundary of the pad to expose aplurality of portions of the upper surface of the upper metal layer ofthe pad, the pattern spanning across the first stack and the secondstack, the plurality of openings configured to distribute a compressiveforce on the upper metal layer, the pattern including a plurality ofstrips in a horizontal direction and a plurality of strips in a verticaldirection within the peripheral boundary, the plurality of strips in thehorizontal direction and the plurality of strips in the verticaldirection forming the plurality of openings, the upper metal layerextending continuously below the plurality of strips in the horizontaldirection and the plurality of strips in the vertical direction, theplurality of openings configured in a plurality of rows and columns, arow or a column adjacent to the peripheral boundary having feweropenings than a row or a column not adjacent to the peripheral boundary.2. The stack structure of claim 1 further comprising a metal bumpimplemented over the pad such that the metal bump is connected to theexposed plurality of portions of the upper surface of the upper metallayer through the plurality of openings of the second portion of thepassivation layer.
 3. The stack structure of claim 2 wherein the firststack includes another metal layer and another polymer layer such thatthe other polymer layer is between the first metal layer and the othermetal layer.
 4. The stack structure of claim 3 wherein the other metallayer is below the first metal layer.
 5. The stack structure of claim 3wherein the polymer layer forms an interface with the other polymerlayer.
 6. The stack structure of claim 2 wherein the pattern definingthe plurality of openings is configured to function as a strap or a netover the upper metal layer to thereby provide the compressive force onthe upper metal layer.
 7. The stack structure of claim 6 wherein thestrap or the net of the pattern is substantially contiguous around theplurality of openings.
 8. The stack structure of claim 2 wherein thesubstrate is a semiconductor substrate.
 9. The stack structure of claim8 wherein the semiconductor substrate is a flip-chip substrate.
 10. Thestack structure of claim 9 wherein the pad is a bump pad.
 11. The stackstructure of claim 8 wherein the semiconductor substrate is a base waferlayer having an integrated circuit.
 12. The stack structure of claim 11wherein the stack structure is configured to form a ring on the basewafer layer, the ring defining an inner area dimensioned to accommodatea device, the ring further configured to allow mounting of a cap waferto substantially enclose the inner area.
 13. A method for fabricating astack structure, the method comprising: providing a substrate; forming apad on the substrate such that the pad includes a first stack includinga first metal layer and a second stack including a second metal layer,the pad further including a polymer layer having a lower surface thatforms an interface with the first metal layer of the first stack and thesecond metal layer of the second stack, and having a wall on a side ofthe polymer layer, the pad further including an upper metal layer overthe polymer layer, the upper metal layer having an upper surface onwhich to implement a metal bump and having a wall on a side of the uppermetal layer; forming a first portion of a passivation layer, the firstportion configured to cover the wall of the upper metal layer and tocover the wall of the polymer layer, the first portion extendingdownward following the shape of the wall of the upper metal layer andthe wall of the polymer layer; and forming a second portion of thepassivation layer over the upper metal layer, the second portion of thepassivation layer including a pattern defining a plurality of openingsin the second portion of the passivation layer within a peripheralboundary of the pad to expose a plurality of portions of the uppersurface of the upper metal layer of the pad, the pattern spanning acrossthe first stack and the second stack, the plurality of openingsconfigured to distribute a compressive force on the upper metal layer,the second portion of the passivation layer including a plurality ofstrips in a horizontal direction and a plurality of strips in a verticaldirection within the peripheral boundary, the plurality of strips in thehorizontal direction and the plurality of strips in the verticaldirection forming the plurality of openings, the upper metal layerextending continuously below the plurality of strips in the horizontaldirection and the plurality of strips in the vertical direction, theplurality of openings configured in a plurality of rows and columns, arow or a column adjacent to the peripheral boundary having feweropenings than a row or a column not adjacent to the peripheral boundary.14. The method of claim 13 further comprising forming a metal bump overthe pad such that the metal bump is connected to the exposed pluralityof portions of the upper surface of the upper metal layer through theplurality of openings of the second portion of the passivation layer.15. A radio-frequency apparatus comprising: a base wafer having anintegrated circuit configured to provide radio-frequency functionality;a cap wafer implemented over the base wafer; and a ring structureimplemented to join the cap wafer to the base wafer to yield a hermeticcavity, the ring structure including a pad, the pad including a firststack including a first metal layer and a second stack including asecond metal layer, the pad further including a polymer layer having alower surface that forms an interface with the first metal layer of thefirst stack and the second metal layer of the second stack, and having awall on a side of the polymer layer, the pad further including an uppermetal layer over the polymer layer, the upper metal layer having anupper surface on which to implement a metal ring and having a wall on aside of the upper metal layer, the ring structure further including apassivation layer including first and second portions, the first portionconfigured to cover the wall of the upper metal layer and to cover thewall of the polymer layer, the first portion extending downwardfollowing the shape of the wall of the upper metal layer and the wall ofthe polymer layer, the second portion implemented over the upper metallayer, the second portion of the passivation layer including a patterndefining a plurality of openings in the second portion the passivationlayer within a peripheral boundary of the pad to expose a plurality ofportions of the upper surface of the upper metal layer, the patternspanning across the first stack and the second stack, the plurality ofopenings configured to distribute a compressive force on the upper metallayer, the pattern including a plurality of strips in a horizontaldirection and a plurality of strips in a vertical direction within theperipheral boundary, the plurality of strips in the horizontal directionand the plurality of strips in the vertical direction forming theplurality of openings, the upper metal layer extending continuouslybelow the plurality of strips in the horizontal direction and theplurality of strips in the vertical direction, the plurality of openingsconfigured in a plurality of rows and columns, a row or a columnadjacent to the peripheral boundary having fewer openings than a row ora column not adjacent to the peripheral boundary, the ring structurefurther including a metal ring implemented over the pad such that themetal ring is connected to the exposed plurality of portions of theupper surface of the upper metal layer of the pad through the pluralityof openings of the second portion of the passivation layer.
 16. Theradio-frequency apparatus of claim 15 further comprising a deviceimplemented within the hermetic cavity.
 17. The radio-frequencyapparatus of claim 16 wherein the device is built on, or a part of, theintegrated circuit of the base wafer.
 18. The radio-frequency apparatusof claim 17 wherein the device is a MEMS device.
 19. The radio-frequencyapparatus of claim 16 wherein the device is a surface acoustic wave(SAW) device, a bulk acoustic wave (BAW) device, or a film bulk acousticresonator (FBAR) device.
 20. The radio-frequency apparatus of claim 19wherein the device is a radio-frequency filter.